1. Field of the Invention
The present invention relates to a water feed device for supplying drinking water to small animals for experimental purposes, such as mice or rats, kept in a small animal rearing apparatus.
2. Description of the Related Art
Generally, a small animal rearing apparatus is used for keeping small laboratory animals, such as mice or rats, to save rearing labor and to use space effectively. The small animal rearing apparatus has a plurality of shelves disposed one upon another to form a vertical arrangement of rearing cage storing spaces. Water feed pipes included in water feed devices are arranged in rearing cage storage spaces so as to project into rearing cages, respectively, to feed drinking water to small animals kept in the rearing cages.
A prior art water feed device disclosed in, for example, U.S. Pat. No. 4,346,672 issued Aug. 31, 1982 has an elongate water feed member, such as a pipe or a rod, having a fore end portion and a base end portion, and a normally closed automatic closing valve connected to the base end portion of the water feed member. When a small animal touches the fore end portion of the water feed member with its nose or mouth so as to tilt the water feed member, the automatic closing valve is opened and water supplied from a water source flows along the water feed member to enable the small animal to drink water.
In this prior art water feed device for a small animal rearing apparatus, the water feed member is sheathed in an sheathing pipe to prevent water dripping from the fore end portion of the water feed member from dropping into the cage. Mischievous small animals confined in the cage often throw or carry intentionally litter, food and/or dirt scattered in the cage into an annular space between the water feed member and the sheathing pipe and, sometimes, play with the litter, food and/or dirt stuffed in the annular space.
When the annular space is stuffed with litter or the like, the fore end portion of the water feed member is dislocated, the water feed member is tilted, the automatic closing valve is opened and water continues to flow wastefully into the cage. Even if the sheathing pipe surrounding the water feed pipe is tilted so as to decline toward the outside of the cage to prevent water from flowing into the cage, the flow of water toward the outside of the cage is obstructed by litter and the like stuffed in the annular space and, consequently, the cage is flooded with water. Litter and the like swell unexpectedly greatly when wet and the swollen litter and the like fill up the annular space completely. Furthermore, if the small animals repetitively push litter and the like into the annular space, playing therewith, the litter and the like are thrust deep into the annular space and reach a coil spring provided for the automatic closing valve. If this occurs, the elastic force of the coil spring becomes entirely or partly ineffective because the litter and the like are thrust into the spaces between the convolutions of the coil spring. Then, the automatic closing valve is kept open and water continues to flow into the cage.
On the other hand, if the annular space is stuffed with litter and the like, they hinders free movement of the water feed member so that the water feed pipe becomes unable to tilt. If this occurs, water is not supplied and small animals are not unable to drink water. This is a serious problem.
On the other hand, if the annular space is stuffed with litter and the like to an extent that permits the movement of the water feed member to enable feeding water, water flows through the litter and the like stuffed in the annular space before the same is fed to the small animals, which is very unsanitary and contaminates water.
Furthermore, the prior art water feed member is relatively slender and weak at the base end, so that water leakage tends to occur at the base end and moreover the base end tends to be disconnected due to shocks imparted thereto by small animals, the forces given by mischievous hanging of small animals from the water feed member, shocks and forces imparted to the water feed member by persons when changing the cages, feeding the animals, cleaning the cages and so on, moving the rearing apparatus and its components, sterilizing the cages and other associated components, etc.
The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a water feed device for a small animal rearing apparatus, which is capable of properly, safely, and sanitarily feeding water even if the water feed device has an opening which can be stuffed mischievously with litter, food or dirt by small animals and which is strong against outer forces and shocks.
According to one aspect of the present invention, a water feed device for a small animal rearing apparatus comprises: an elongate water feed member having a fore end portion to be touched by a small animal and a base end portion opposite the fore end portion; a sheathing pipe sheathing the water feed member therein so as to define a thin annular space surrounding the water feed member; a closing valve having an inlet side connected to a water source and an outlet side connected to the water feed member; and a protective pipe coaxially receiving the sheathing pipe therein so as to define a thick annular space surrounding the sheathing pipe and having a thickness greater than that of the thin annular space. In this water feed device, the closing valve includes a holding means holding the base end portion of the water feed member to hold the water feed member at a valve closing position and to enable the water feed member to turn on the base end portion to a valve opening position when a small animal touches the fore end portion of the water feed member, the closing valve is closed when the water feed member is at the valve closing position and is open to enable water to flow along the water feed member toward the fore end portion of the same when the water feed member is tilted to the valve opening position.
The protective pipe may comprise a plurality of coaxially nested pipes.
Preferably, the thickness of the thin annular space surrounding the water feed member is in the range of 2 to 3 mm, and the thickness of the thick annular space surrounding the sheathing pipe is in the range of 6 to 9 mm.
The thick annular space between the sheathing pipe and the protective pipe is an attractive space for a mischievous small animal to put foreign matters in, and the small animal will not try to put foreign matters in the thin annular space between the water feed member and the sheathing pipe.
Since the water feed member is protected by the sheathing pipe, and the sheathing pipe is protected by the protective pipe, the safety of the water feed device is enhanced, and the water feed member and the sheathing pipe are protected from shocks that may be exerted thereon by small animals and those that may be exerted thereon by the attendants engaged in work with the rearing cage and so on.
The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings.